Buggy code:
public abstract class Session implements Serializable { public static final String SESSION_ATTRIBUTE_NAME = "session" ; private static final char COMPONENT_PATH_SEPERATOR = ':' ; private static final ThreadLocal CURRENT = new ThreadLocal ( ) ; private static final Log log = LogFactory . getLog ( Session . class ) ; private transient Application application ; private ClientInfo clientInfo ; private transient IConverter converter ; private transient boolean dirty = false ; short accessSequenceNumber ; private List listeners = new ArrayList ( ) ; private Locale locale ; private transient IPageFactory pageFactory ; private String style ; private final String pageMapAttributePrefix = "m:" ; final String pageSourceAttributePrefix = "p:" ; static interface IVisitor { public void pageMap ( final PageMap pageMap ) { } } public static Session get ( ) { } public static void set ( final Session session ) { if ( session == null ) { <START_BUG> throw new NullPointerException ( "argument<seq2seq4repair_space>session<seq2seq4repair_space>must<seq2seq4repair_space>me<seq2seq4repair_space>not<seq2seq4repair_space>null" ) ; <END_BUG> } Session . CURRENT . set ( session ) ; } protected Session ( final Application application ) { } public void add ( ISessionAttributeListener listener ) { } public final Application getApplication ( ) { } public final IClassResolver getClassResolver ( ) { } public ClientInfo getClientInfo ( ) { } public final IConverter getConverter ( ) { } public String getId ( ) { } public Locale getLocale ( ) { } public final Page getPage ( final String pageMapName , final String path , final int versionNumber ) { } public final IPageFactory getPageFactory ( ) { } public final IPageFactory getPageFactory ( final Page page ) { } public final PageMap getPageMap ( String pageMapName ) { } public final RequestCycle getRequestCycle ( ) { } public final String getStyle ( ) { } public final void init ( ) { } public abstract void invalidate ( ) { } public final PageMap newPageMap ( final String name ) { } public final RequestCycle newRequestCycle ( final Request request , final Response response ) { } public void remove ( ISessionAttributeListener listener ) { } public final void remove ( final Page page ) { } public final void removeAll ( ) { } public final void setApplication ( final Application application ) { } public final void setClientInfo ( ClientInfo clientInfo ) { } public final void setLocale ( final Locale locale ) { } public final void setStyle ( final String style ) { } public void touch ( Page page ) { } protected void attach ( ) { } protected void detach ( ) { } protected final void dirty ( ) { } protected abstract Object doGetAttribute ( String name ) { } protected abstract void doRemoveAttribute ( String name ) { } protected abstract void doSetAttribute ( String name , Object value ) { } protected final void fireAttributeAdded ( String name , Object value ) { } protected final void fireAttributeRemoved ( String name ) { } protected final void fireAttributeReplaced ( String name , Object value , Object oldValue ) { } protected final Object getAttribute ( final String name ) { } protected abstract List getAttributeNames ( ) { } protected final List getListeners ( ) { } protected abstract IRequestCycleFactory getRequestCycleFactory ( ) { } protected final void removeAttribute ( String name ) { } protected final void setAttribute ( String name , Object value ) { } protected void update ( ) { } final void access ( IPageSource pageSource ) { } final Page getPage ( final String pageMapName , final int id ) { } final void removePageMap ( final PageMap pageMap ) { } final void visitPageMaps ( final Session . IVisitor visitor ) { } private final String attributeForPageMapName ( final String pageMapName ) { } }

Fix:
throw new IllegalArgumentException ( "Argument<seq2seq4repair_space>session<seq2seq4repair_space>must<seq2seq4repair_space>me<seq2seq4repair_space>not<seq2seq4repair_space>null" ) ;